This invention relates generally to dead bolt lock sets which are employed to secure doors. More particularly, the present invention relates generally to dead bolt lock sets wherein the dead bolt is projectable to an extended position in the strike of the door.
Conventional dead bolts are typically employed alone or in combination with self-latching latch bolts to secure a doorway. The self-latching latch bolt typically has a beveled latch bolt and a spring for biasing the latch bolt in the extended position. Self-latching latch bolts provide the advantage of automatically latching the door when it is closed, and with certain lock mechanisms, automatically locking the door under such circumstances.
Conventional spring biased latch bolts, however, are susceptible to tampering to allow unauthorized access. Tools or other slim items can be slipped between the door and the door frame to engage the beveled edge of the latch and force the latch bolt back into the latch set, thereby allowing the door to be opened. III-fitting doors, or doors that warp or change over time, can become more susceptible to this form of tampering.
Dead bolts have been employed to overcome some of these deficiencies. Dead bolts typically define a squared-off end that is less susceptible to tampering than the beveled end of a typical self-latching latch bolt set. Furthermore, dead bolts are typically not spring loaded, therefore maintaining the dead bolt in an extended position until the lock mechanism is employed to retract it. In addition, dead bolts typically have a longer throw or extension of the bolt for additional locking strength. A deficiency of dead bolts is that they must typically be manually engaged. Furthermore, a dead bolt is usually paired with a self-latching latch bolt, thereby requiring an additional opening in the strike for reception when the door is in the closed position.